Apparatus for casting metal under pressure



Nov. 2-2, 1938. K. F. WAGNER 2,137,764

APPARATUS FOR CASTING METAL UNDER PRESSURE Filed March 4, 1937 2Sheets-Sheet 1 Nov. 22, 1938. K. F. WAGNER Y APPARATUS FOR CASTING METALUNDER PRESSURE Filed March 4, 1937 2 Sheets-Sheet 2 Patented Nov. 22,1938 I 2,137,754 APPARATUS FOR CASTING METAL UNDER PRESSURE KarlFriedrich Wagner, Friedrichshai'en,

Bod

ensee, Germany Application March 4", 1937, Serial No. 128,896 In GermanyMarch 19, 1936 3 Claims.

My invention relates to the casting of metals and more especially tomeans for casting metal under pressure in permanent metal molds, asdescribed for instance in my copending application for Letters Patent ofthe United States Serial No. 124,978, filed February 10, 1937, theseapparatus being particularly useful when casting readily oxidizablemetals such as magnesium and its alloys.

I have described an apparatusin which the pres-' sure chamber isdirectly combined with a filling chamber partly submerged in the meltingpot, this system being delimited on one side by the pressure piston, onthe other side by a counterpiston, which can be withdrawn altogether forthe purpose of expelling the waste metal from the pressure chamber. Inall cases the casting metal in the pressure chamber is compressed bymeans of a single pressure piston.

I have now found that I can obtain a better and quicker pressing eifect,if the metal enclosed in the pressure chamber before compression isforced towards the pistons simultaneously, which are moved in op-,posite directions. In contradistinction to the apparatus disclosed inmy copending applications, the pressure chamber is here delimited by atleast two movablepistons which at the start of the pressure operationare spaced equally from the gate and are moved toward the gate inopposite sense and under equal pressure and with velocities such that.the casting metal is forced at high speed through thegate into the moldand that, when the pistons have reached the end of their stroke, thewaste metal islocated below the gate. I prefer imparting to the pistonmoving above the filling chamber a certain lead relative to thecounter-piston from its outer end position up to the position in whichit covers the point where the filling cylinder joins the pressurechamber. In this position the two inner end faces of the two pistons arespaced equally from the center of the gate. Fromthis point on the twopistons are moved towards the gate in a uniform manner, preferably by acommon source of energy and by means of a coinon control.

I have taken care that themovements of the two pistons, occur inabsolute relative dependency in such manner that the influence offrictional resistances of different degree, which might arise gate by aplurality of pressure I lated in a well known manner.

during the sliding of the pistons in the pressure chamber and betweenthe driving members is paralyzed by the selection of suitableconstructions and an exact distribution of forces. Thus for instance thetwo opposed pistons may be connected with each other in the usual mannerby a system of levers, with the aid of which the compression movement aswell as. the return movement can be started by means of eccentric disksorcams mounted on a driving shaft which is driven by some suitablesource of power. I may however also drive the two pistons in bothdirections by means of stationary power cylinders and a system oflevers. Since these driving means are of a well known kind, it does notappear necessary to enter into a detailed description thereof. I havefound the hydraulic drive to be the most suitable for the purpose ofthis invention, as it allows of controlling the operation of the twopistons in the simplest manner.

As mentioned above, it is essential that the movements of the pistonsare controlled exactly and altogether positively in order to providethat uniform quantities of casting metal be always displaced from thepressure chamber by the two pistons. I thus obtain that the waste metalis .kept as small as possible and for the same purpose care is taken toarrange the runner midways of the waste metal.

I further provide the two pistons with adjustable means for limitingtheir stroke in order to prevent the pistons from passing beyond theirend positions relative to the gate.

I prefer cooling the pressure pistons by means of water or some othersuitable liquid supplied to cavities provided in the pistons throughborings, the-circulation of the cooling liquid being regu- I thus avoidany accumulation of heat and consequent undesirable expansion of thepistons.

In 'the drawings afiixed to this specification and forming part thereofa casting device embodying my invention is illustrated diagrammaticallyby way of example.

In the drawings Fig. 1 is a vertical section of the smelting oven withthe casting device disposed on top of it, while Figs. 2 to 7 illustratethe coaction of the two pressure pistons in the pressure chamber intheir most important positions.

Fig. 2 is a longitudinal section of the pressure chamber showing thefilling chamber filled with molten metal. a

Fig. 3 is a similar view showing the same parts after the pressurechamber has been filled with metal.

Fig. 4 illustrates the position of the parts at the beginning of thecompression operation.

Fig. 5 shows the position of the pistons at the end of the operation.

Fig. 6 shows the position of the parts, while the waste metal is beingexpelled.

Fig. 7 shows their position during their return strokes and Fig. 8illustrates on a larger scale the relative position of the waste metaland the runner.

Referring to the drawings and flrst to Fig. 1. ll is a smelting oven and2| the melting pot filled with a body 22 of molten metal. 28 is the ovencover and 21 is a case forming part of the cover and enclosing the metalfeeding and compressing means. I is a cylinder extending downwardly fromthe pressure chamber into the molten metal, this cylinder being formedwith a lateral intake opening 9. 3 is the filling piston reclprocable inthis cylinder by means of rods I4 governed by a piston 33. I is thecylinder forming the pressure chamber in communication with the flllingcylinder 8 and I and 2 are two pistons reciprocable in the pressurechamber, being governed by pistons SI and 32, respectively. I is thegate leading to the riser 35 formed in the mold 23 which is seated ontop of. the pressure chamber and is closed by a cover 24 gove'rned by apiston 26. 3!

is a cooling or heating jacket surrounding the pressure chamber 34.

The pressure piston 2 is shown in Fig. 2 in its extreme end position,which is spaced a distance from the inner edge of the mouth 4 of thefllling cylinder 4 in the pressure chamber 1. In order to make thepiston stroke as short as pos sible, the mouth 4 is partly covered bythe piston 2 already in the extreme position of the piston.

The filling piston 3 now moves upwardly, cover-.

ing first of all the intake opening and lifting the metal I4 in thecylinder into the pressure chamber I (Fig. 3). After the metal hasentered the space left between the two pistons in the pressure chamber,the piston 2 is started in the direction towards the gate 5, completelycovering the mouth 4 (Fig. 4). When the piston 2 has moved into thisposition, the gate 5 is located exactly in the middle of the space IIIwhich is now delimited by the two pistons I and 2 (Fig. 4).

From this moment on the two pistons move in opposite-directions towardsthe gate 5 and compress the metal between them. The velocity of the twopistons during this movement is equal and so are the lengths of strokeand the pressures required for the compression.

Bythe control system indicated at 4| in Fig. 1 the two pistons are soconnected with each other, that during the pressing operation theyalways move together and simultaneously, being driven either byhydraulic or by mechanical means.

On the mold having been filled through the gate I, the pistons I. and 2come to a stillsiiand and now take up the positions shown in Fig. 5.Since the two pistons have carried out the compression work altogetheruniformly, the runner I I now takes up exactly a position in the middleof the waste metal I! (Fig. 8).

In order to prevent the two pistons from moving beyond the desired endpositions, stroke limiting devices are provided, as shown for instancein Fig. 2, where II is a collar mounted on the piston rod II andabutting in its end position against stops it fixed to the machineframe, whereby the piston, is stopped when the waste metal has reached apredetermined minimum thickness.

The piston I is now moved outwardly, the piston 2 following it in thesame direction until it has exp lled the waste metal I2 from thepressure chamber (Fig. 6) Now first the piston I and thereafter alsopiston 2 move towards the right (Fig. 7) until the two pistons havereached their initial positions shown in Fig. 2.

In order to accurately control the temperature of the pistons, inflowand outflow conduits I1, I8 are formed in the piston rods and pistons,throug which a suitable cooling or heating agent may be;

passed (Fig. 3).

A material advantage of this combination of the pistons as compared withthe devices disclosed in my copending applications consists therein,that in contrast to the apparatus operated by a single piston the pistonstroke, when two pistons are provided, is reduced to one half and in thecase of more than two pistons to a corresponding fraction. Furthermorethe outflow velocity of the metal through the gate is greatly increasedat equal piston velocities. This design further involves a. smalleroverall length of the apparatus, in consequence of which also the partsenclosing the pressure chamber can be made smaller and lighter.

Obviously this casting apparatus is not limited to the casting ofmagnesium or its alloys, but may be used with equal advantage in thecasting of other metals and alloys.

The gate 5 which connects the pressure chamber I with the mold may bearranged above, laterally of or obliquely to and at any desired anglerelative to the pressure chamber. The pistons I', 2 and I and the powercylinders driving them are actuated by means of-a common controllingsystem H at a predetermined rate.

I wish it to be understood that I do not desire to be limited to theexact details of construction shown and described for obviousmodifications will occur to a person skilled in the art.

I claim:-

1. A metal casting apparatus comprising in combination, a cylinderforming a pressure chamber, two opposed pistons arranged in said chamberfor reciprocation in opposite directions,

means for feeding molten metal into said chamber intermediate saidpistons, a gate formed in the wall of said cylinder and means forholding said pistons equally spaced from said gate before compressionbegins, and for moving same towards said gate with equal pressures andspeeds.

2. The metal casting apparatus of claim 1, m which the gate is locatedin the middle of the pressure chamber between'the inner edge of themouth of the fllling cylinder and the outer end position of the outerpressure piston.

3. A metal casting apparatus comprising in combination a melting pot, acylinder forming a pressure chamber secluded from air arranged outsidesaid melting pot, two opposed pistons arranged in said chamber forreciprocation in opposite directions, a cylinder forming a flllingchamber secluded from air associated with and opening into said pressurechamber, a gate formed in the wall of said pressure chamber intermediatesaid filling chamber and one of said pistons, means for moving, in thestarting operation, the other, pressure, piston until it covers theopening of said fllling chamber and means for thenmoving both pistons inopposite direction and about an equal distance toward said gate;

KARL FRENCH WAGNER.

